media-viewer: disconnect the keypress signal on unmap

We were storing the signal_id, but we never disconnect that handler so
it worked the first time and then we were getting all key events and
future widgets creation doesn't work.

This patch disconnect the signal just when the widget gets unmapped, as
we create a new widget when we open the media-viewer again.

Fix #402

fractal-gtk/src/widgets/media_viewer.rs

@@ -625,18 +625,6 @@ impl MediaViewer {
         next_media_button.connect_clicked(move |_| {
             own.borrow_mut().next_media();
         });
-        let back = self
-            .builder
-            .get_object::<gtk::Button>("media_viewer_back_button")
-            .expect("Can't find media_viewer_back_button in ui file.");
-        let previous_media_button = self
-            .builder
-            .get_object::<gtk::Button>("previous_media_button")
-            .expect("Cant find previous_media_button in ui file.");
-        let next_media_button = self
-            .builder
-            .get_object::<gtk::Button>("next_media_button")
-            .expect("Cant find next_media_button in ui file.");
         let full_screen_button = self
             .builder
             .get_object::<gtk::Button>("full_screen_button")
@@ -657,8 +645,7 @@ impl MediaViewer {
                             }
                         }
 
-                        back.clicked();
-                        Inhibit(true)
+                        Inhibit(false)
                     }
                     gdk::enums::key::Left => {
                         previous_media_button.clicked();
@@ -672,6 +659,16 @@ impl MediaViewer {
                 }
             });
         self.data.borrow_mut().signal_id = Some(id);
+
+        // Remove the keyboard signal management on hide
+        let data = self.data.clone();
+        media_viewer_box.connect_unmap(move |_| {
+            let id = data.borrow_mut().signal_id.take();
+            let main_window = &data.borrow().main_window;
+            if let Some(id) = id {
+                signal::signal_handler_disconnect(main_window, id);
+            }
+        });
     }
 }